The present invention is related to a thin-film forming method which can form a thin film with an improved evenness.
With the progresses of IC manufacturing methods, the aspect ratio of a multilayer semiconductor device increase as the integrated density increases. As a result, a thin-film forming method with an improved gap-filling ability is getting more and more attention.
FIG. 1 schematically shows a conventional high density plasma chemical vapor deposition (HDPCVD) method which is wildly used by semiconductor manufacturers nowadays. The HDPCVD utilizes instantaneously depositing and etching steps to improve the gap-filling ability of a thin film. For example, as shown in FIG. 1(a), when a SiO2 thin film 12 is deposited from silane (SiH4) and oxygen (O2) on a topographically rugged substrate 10 which has a device structure 11 thereon, a bias radiofrequency (bias RF) is instantaneously used to accelerate ions (such as argon, helium or oxygen ions) in the plasma to ion bomb the SiO2 thin film 12. Therefore, the burs of the thin film 12 formed around the voids and gaps are destroyed by the ion bombing and the crashed dregs are filled into the voids and gaps, as shown in FIG. 1(b).
As described above, the HDPCVD can effectively improved the gap-filling ability of a thin film on a topographically rugged substrate, but many triangle peaks will be left, as shown in FIG. 1(c). The triangle peaks cannot be easily ground to be flat by the chemical mechanical polishing (CMP) because the grinding solution 13 is trapped in the concave grooves between the triangle peaks (the grinding solution 13 can not distribute uniformly). Therefore, the grinding time of CMP needs to be extended, otherwise the grinding effect of CMP will be poor.
It is therefore attempted by the present applicant to deal with the above situation encountered with the prior art.
An object of the present invention is to provide a novel thin-film forming method applied in an IC manufacturing process for forming a thin film with an improved evenness. The method includes the step of (a) forming a thin film on a topographically rugged substrate, (b) ion bombing the thin film to improve a gap-filling ability of the thin film, (c) after the thin-film forming step is finished, ion bombing the thin film continuously for a specific time to improve the evenness of the thin film.
According to the present invention, the thin film is formed by a chemical vapor deposition method, preferably the high density plasma chemical vapor deposition method.
The thin film of the present invention is a silicide layer, preferably a SiO2 layer. The thin film is ion bombed by using a bias radio-frequency to accelerate ions in a plasma, and the ions are argon, helium or oxygen ions.
According to the present invention, the depositing step and the ion bombing step are processed in the same machine.
The present invention may best be understood through the following description with reference to the accompanying drawings, in which: